GA Flood Risk & Social Vulnerability

An Exploration of County & Census Tract Impacts

Shikha Srinivas, Community Resilience Data Intern, Re:Public; Justin Cross, Data Science Intern, Re:Public; Max Evans, Head of Product and Geospatial Data, Re:Public

This virtual link is meant to supplement Re:Public’s poster at the 2021 Georgia Climate Conference. It contains interactive graphics which included screencaps on the poster as well as a few additional charts.

The datasets used include the National Flood Hazard Layer for a 100-year flood by extent, the CDC’s Social Vulnerability Index (1), and Re:Public’s database of flooded community lifelines (accessed December 2020).

Flood Claims in GA

The map below shows the number of flood claims by tract.

The table below shows the counties with the most flood claims in the last ~50 years.

county tract_claims building_claims
Chatham 5173 3664
Fulton 2830 2153
DeKalb 1942 1367
Glynn 1894 1277
Cobb 1819 1320
Dougherty 1239 953
Lee 648 551
Richmond 498 388
Gwinnett 468 351
Floyd 374 273

County Flooding and SVI

The interactive map below shows the CDC’s SVI overall vulnerability percentile (ranked at the national level) by county.

The table shows the 10 most vulnerable counties in the state.

county vulnerability_percetile
Mitchell County, Georgia 0.9879
Crisp County, Georgia 0.9857
Evans County, Georgia 0.9847
Candler County, Georgia 0.9828
Colquitt County, Georgia 0.9812
Turner County, Georgia 0.9809
Clinch County, Georgia 0.9777
Calhoun County, Georgia 0.9774
Emanuel County, Georgia 0.9768
Sumter County, Georgia 0.9764

The following scatterplot shows how overall vulnerability (percentiles taken at the national level) compares to county area flooded.

The interactive map below shows county and percent flooding by land area.

The list below outlines the 10 most flooded counties by land area in Georgia.

county area_flooded_percentage
Chatham 59.70837
Liberty 58.02474
McIntosh 57.64067
Bryan 56.55048
Glynn 52.41560
Ware 52.30268
Long 51.33037
Charlton 49.60163
Clinch 49.17702
Camden 45.50368

The map below shows the percent of community lifelines (critical infrastructure) in the floodplain of a 100-year flood by county.

The list below the counties experiencing the largest amount of infrastructure flooding.

county lifelines_impacted_percentage
Rabun 46.00000
Gilmer 40.22989
Fannin 39.28571
Stewart 39.07285
McIntosh 38.75000
Pulaski 38.46154
Oglethorpe 37.81513
Colquitt 37.54789
Worth 36.89320
Clinch 35.05155

The following maps show impacted lifelines by type and county for the top 5 most well-defined community lifelines in FEMA’s dataset.

county percent_communication_infrastructure_flooded
Bryan 34.04255
Seminole 31.57895
Miller 30.00000
Cook 26.82927
Chatham 23.00885
county percent_energy_infrastructure_flooded
Rabun 33.33333
Gilmer 31.25000
Worth 25.00000
Union 25.00000
Glynn 21.27660
county percent_health_medical_infrastructure_flooded
Pulaski 28.57143
Appling 20.00000
Jeff Davis 20.00000
Chatham 17.02128
Gordon 11.11111
county percent_safety_security_infrastructure_flooded
Chattooga 31.03448
Murray 26.53061
Appling 20.38835
Toombs 20.00000
Muscogee 17.49271

Given the scale at which transportation infrastructure is impacted at the state level, the top 10 are included below.

county percent_transportation_infrastructure_flooded
Oglethorpe 85.71429
Pulaski 82.22222
McIntosh 73.41772
Rabun 72.07207
Baker 70.83333
Heard 69.23077
Stewart 68.23529
Bacon 58.49057
Clay 57.69231
Worth 57.29730

Land Area and Lifelines Flooding Relationship

Using Re-Public community lifeline flooding data at the county level, we wanted to assess the relationships between land area flooded and lifeline flooding.

There is little correlation between the two parameters (R^2 = 0.08651). While some of the coastal counties face very flood risk by land area, inland counties with high social vulnerability (ex. Colquitt) may deal with a large loss of critical infrastructure.

Tract Flooding & SVI

The interactive map displays social vulnerability of every tract (ranked at the state level).

The following plot shows tract-level land area flooding.

This plot shows the relative population affected (using % flooding as the proportion for population affected).

For every tract, we calculated a combined social vulnerability-flooding score by multiplying the vulnerability percentile (ranked at the state level) with the tract flooding. This graphic shows the scores from the overall vulnerability percentile.

References

  1. Centers for Disease Control and Prevention/ Agency for Toxic Substances and Disease Registry/ Geospatial Research, Analysis, and Services Program. CDC/ATSDR Social Vulnerability Index [2018] Database [Georgia].